The present invention relates generally to digital circuitry. In particular, the present invention is a digital correlator which performs digital correlation on two digital words.
Digital correlators have found application in a variety of different digital systems. Examples of prior art digital correlators are shown in U.S. Pat. Nos. 3,646,333 by Pryor, Jr.; 3,670,151 by Lindsay et al; 3,717,756 by Stitt; 3,725,689 by Kautz; 3,881,101 by Pederson et al; and 3,942,022 by Stumpf et al.
One application which requires a digital correlator is the digital auto-focus system described in the above-mentioned co-pending application by Norman L. Stauffer. In this auto-focus system, two digital words of equal length are produced by two detector arrays. Signal processing circuitry, including a digital correlator, determines the number of bits by which the second word is displaced with respect to the first word. This number may be used to position the taking lens of a camera.
For purposes of the system described in the Stauffer application, the digital correlator must be relatively simple and low-cost and use a small number of components. The digital correlator cannot be a high cost item, since this would adversely affect the overall cost of the camera into which it will be incorporated.